NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 21 



determinate lateral ultimately deciduous; gland cells absent; repro- 

 duction unknown. 



Type: Holotype is E. Y. Dawson 6934b, March 15, 1949, in Herb. 

 Allan Hancock Foundation. 



Type locality: San Lorenzo Channel, Baja California, dredged 

 from 8-20 m. 



The tendency of the secondary branchlets from the subspherical 

 basal cell of the primary determinate branches to grow around the 

 indeterminate axis like a loose cortication distinguishes this species from 

 all known species of Antithamnion and is suggestive of the more 

 profusely compacted cortication of A. cladodermum (Zan.) J. Ag. (see 

 Funk, 1955, p. 110, fig. 4, 5, 6). The only other corticated species of 

 Antithamnion known is A. corticatum Tokida (1932, p. 109, pi. Ill), 

 and in this one only a few ultimate laterals grow parallel and appressed 

 to the indeterminate axis. The close, symmetrical, distichous branching 

 is also distinctive. 



Antithamnion pygmaeum Gard. 

 PI. 6, fig. 2 

 Gardner 1927b, p. 413, pi. 91, 92, 93; Dawson 1949, p. 26; Dawson, Neushul 

 & Wildman 1960a, p. 24 (partly as A. kylinii) 



Thalli minute, fragile, 4-7 mm high, attached by a branched 

 discoid base, in part prostrate and attached by compound rhizoids 3-4 

 cells long arising from the basal cell of a branch and becoming discoid 

 at their distal ends; main axes percurrent, sparingly branched, 50-75 ti 

 in diameter at the base, tapering very gradually to the apices; main 

 axes and branches clothed with paired, opposite, determinate ramuli 

 from every cell, but without such a ramulus opposite an indeterminate 

 main branch; determinate ramuli, becoming more or less recurved, 

 composed of 6-10 cylindrical cells 24-28 /x in diameter, 2-2.5 diameters 

 long, except the subspherical basal cne, giving rise adaxially to 6-8 

 secund, somewhat outwardly curved, ultimate ramuli; subspherical 

 basal cell often bearing a diminutive indeterminate branch; tetraspor- 

 angia ellipsoidal, 75-80 ti long, terminal or lateral and sessile (sometimes 

 apparently pedicellate) on short adaxial ultimate branchlets; sperma- 

 tangia forming cylindrical clusters on the adaxial side of the ultimate 

 ramuli; gland cells present on the ultimte ramuli, commonly near the 

 tips and lying along 2 cells. 



Type: Gardner 5090, July, in the Herbarium of the University of 

 California, Berkeley (296663). An isotype is in Herb. A. Hancock 

 Found. 



Type locality: Epiphytic on the stipe of Pelagophycus porra, 

 La Jolla, Calif. 



Mexican distribution: Pacific Baja Calif. — D. 8006, Cortez 

 Bank, 30-40 m.; D. 4266, Isla Coronado del Sur; D. 20480 (Neushul), 



